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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:1
UID:UW-Physics-Event-4969
DTSTART:20190308T213000Z
DURATION:PT1H0M0S
DTSTAMP:20260416T110348Z
LAST-MODIFIED:20190212T191917Z
LOCATION:2241 Chamberlin Hall
SUMMARY:How Much Time Does a Tunneling Atom Spend In The Forbidden Reg
 ion?\, Physics Department Colloquium\, Aephraim Steinberg\, U Toronto
DESCRIPTION:The question of the time a particle takes to tunnel throug
 h a classically forbidden region has a long history\, complicated by t
 he fact that the simplest predictions for the arrival time of a wave p
 acket peak may be smaller than the barrier thickness divided by the sp
 eed of light.  By now it is well understood that this result is not pa
 radoxical\, but it leaves open the question of how long a particle int
 eracts with the barrier\, and of whether it is sensible to distinguish
  between interaction times for transmitted and reflected particles.<br
 >
\n<br>
\nBy preparing ultracold Rubidium atoms in an atom waveguide 
 and cooling them to approximately 1 nK\, we are able to study tunnelin
 g across a 1-μm barrier formed by a blue-detuned laser beam.  Using R
 aman coupling to generate a fictitious magnetic field\, we let the spi
 n of each atom act as a “clock” to record how long it spends in th
 e barrier region.  I will present our first results characterizing the
  tunneling time in this way.  We analyze them in terms of the weak-mea
 surement formalism\, which makes it possible for one to discuss differ
 ent “histories” for particles which end up in different final stat
 es.  I will spend some time discussing this formalism more broadly\, i
 ncluding problems it resolves and puzzles it raises.
URL:https://www.physics.wisc.edu/events/?id=4969
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